Copying Only Files that Have Changed

Oct 13, 2025 by windailys.com 6 views

Introduction

Rsync is a powerful command-line utility that allows you to efficiently copy and synchronize files and directories between two locations. One of its key features is its ability to copy only files that have changed, rather than transferring all files every time. This makes it an ideal tool for backing up data, synchronizing files between multiple machines, and mirroring directories. In this article, we will explore how to use rsync to copy only files that have changed, not files that are new.

Understanding Rsync

Before we dive into the specifics of using rsync to copy only files that have changed, it's essential to understand how rsync works. Rsync uses a technique called "delta encoding" to transfer only the differences between files. This means that if a file has changed, rsync will only transfer the modified parts of the file, rather than the entire file. This approach makes rsync much more efficient than traditional file transfer methods, especially when dealing with large files or many files.

Basic Rsync Command

The basic rsync command is straightforward:

rsync -avz source/ dest/

Here's a breakdown of the options used:

-a stands for "archive" mode, which preserves file permissions, ownership, and timestamps.
-v enables verbose mode, which displays detailed information about the transfer process.
-z compresses the data during transfer, which can help reduce the amount of data transferred.

Copying Only Files that Have Changed

To copy only files that have changed, you can use the --update option, which tells rsync to only transfer files that have been modified since the last transfer. Here's an example:

rsync -avz --update source/ dest/

This command will only transfer files that have changed since the last transfer, rather than transferring all files.

Ignoring New Files

If you want to ignore new files and only copy files that have changed, you can use the --ignore-new option. Here's an example:

rsync -avz --update --ignore-new source/ dest/

This command will ignore new files and only transfer files that have changed.

Using Rsync with a Specific File Pattern

If you want to copy only specific files or directories, you can use the --include and --exclude options. For example, to copy only files with a specific extension, you can use the following command:

rsync -avz --update --include="*.txt" --exclude="*" source/ dest/

This command will only copy files with a .txt extension.

Using Rsync with a Specific File Size

If you want to copy only files of a specific size, you can use the --size-only option. For example, to copy only files larger than 100MB, you can use the following command:

rsync -avz --update --size-only --size-only=100M source/ dest/

This command will only copy files larger than 100MB.

Using Rsync with a Specific File Modification Time

If you want to copy only files that have been modified within a specific time range, you can use the --modify-time option. For example, to copy only files modified within the last 24 hours, you can use the following command:

rsync -avz --update --modify-time=1 source/ dest/

This command will only copy files modified within the last 24 hours.

Conclusion

Rsync is a powerful tool for copying and synchronizing files and directories. By using the --update option, you can copy only files that have changed, rather than transferring all files every time. Additionally, you can use various options to ignore new files, copy specific files or directories, and copy files of a specific size or modification time. With these techniques, you can efficiently manage your files and directories using rsync.

Common Rsync Options

Here are some common rsync options:

-a or --archive: Preserves file permissions, ownership, and timestamps.
-v or --verbose: Displays detailed information about the transfer process.
-z or --compress: Compresses the data during transfer.
--update: Only transfers files that have been modified since the last transfer.
--ignore-new: Ignores new files and only transfers files that have changed.
--include: Includes files or directories that match the specified pattern.
--exclude: Excludes files or directories that match the specified pattern.
--size-only: Only transfers files of a specific size.
--modify-time: Only transfers files that have been modified within a specific time range.

Troubleshooting Rsync

Here are some common issues and solutions when using rsync:

Error: "rsync: failed to set times on": This error occurs when rsync is unable to set the modification time of a file. Try using the --no-times option to disable the modification time check.
Error: "rsync: failed to set permissions on": This error occurs when rsync is unable to set the permissions of a file. Try using the --no-perms option to disable the permissions check.
Error: "rsync: failed to set ownership on": This error occurs when rsync is unable to set the ownership of a file. Try using the --no-owner option to disable the ownership check.

Conclusion

Introduction

Rsync is a powerful command-line utility that allows you to efficiently copy and synchronize files and directories between two locations. With its numerous options and features, rsync can be a bit overwhelming for beginners. In this article, we will answer some of the most frequently asked questions about rsync, covering topics such as basic usage, options, and troubleshooting.

Q: What is rsync?

A: Rsync is a command-line utility that allows you to efficiently copy and synchronize files and directories between two locations. It uses a technique called "delta encoding" to transfer only the differences between files, making it much faster than traditional file transfer methods.

Q: How do I use rsync?

A: The basic rsync command is straightforward:

rsync -avz source/ dest/

Here's a breakdown of the options used:

-a stands for "archive" mode, which preserves file permissions, ownership, and timestamps.
-v enables verbose mode, which displays detailed information about the transfer process.
-z compresses the data during transfer, which can help reduce the amount of data transferred.

Q: What are the most common rsync options?

A: Here are some of the most common rsync options:

-a or --archive: Preserves file permissions, ownership, and timestamps.
-v or --verbose: Displays detailed information about the transfer process.
-z or --compress: Compresses the data during transfer.
--update: Only transfers files that have been modified since the last transfer.
--ignore-new: Ignores new files and only transfers files that have changed.
--include: Includes files or directories that match the specified pattern.
--exclude: Excludes files or directories that match the specified pattern.
--size-only: Only transfers files of a specific size.
--modify-time: Only transfers files that have been modified within a specific time range.

Q: How do I copy only files that have changed?

A: To copy only files that have changed, you can use the --update option:

rsync -avz --update source/ dest/

This command will only transfer files that have been modified since the last transfer.

Q: How do I ignore new files?

A: To ignore new files and only transfer files that have changed, you can use the --ignore-new option:

rsync -avz --update --ignore-new source/ dest/

This command will ignore new files and only transfer files that have changed.

Q: How do I copy specific files or directories?

A: To copy specific files or directories, you can use the --include and --exclude options. For example, to copy only files with a specific extension, you can use the following command:

rsync -avz --update --include="*.txt" --exclude="*" source/ dest/

This command will only copy files with a .txt extension.

Q: How do I troubleshoot common rsync issues?

A: Here are some common issues and solutions when using rsync:

Error: "rsync: failed to set times on": This error occurs when rsync is unable to set the modification time of a file. Try using the --no-times option to disable the modification time check.
Error: "rsync: failed to set permissions on": This error occurs when rsync is unable to set the permissions of a file. Try using the --no-perms option to disable the permissions check.
Error: "rsync: failed to set ownership on": This error occurs when rsync is unable to set the ownership of a file. Try using the --no-owner option to disable the ownership check.

Q: How do I optimize my rsync commands for better performance?

A: Here are some tips to optimize your rsync commands for better performance:

Use the --compress option to compress the data during transfer.
Use the --update option to only transfer files that have changed.
Use the --ignore-new option to ignore new files and only transfer files that have changed.
Use the --include and --exclude options to copy specific files or directories.
Use the --size-only option to only transfer files of a specific size.
Use the --modify-time option to only transfer files that have been modified within a specific time range.

Conclusion

Rsync is a powerful tool for copying and synchronizing files and directories. By understanding the basics of rsync and using the right options, you can efficiently manage your files and directories. With this knowledge, you can troubleshoot common issues and optimize your rsync commands for better performance.